Graphene, an aromatic graphite monolayer first isolated in 20041 has become famous as a highly versatile material with unique properties in terms of mechanical strength, electrical conductivity and thermal conductivity1. Its flexibility makes it perfectly suited for coatings and application in membranes2. All these desired properties are at least partly dependent on the two dimensional structure of the carbon allotrope.
Many approaches to the chemical modification of graphene have been made to fine-tune its electrical properties3, its water solubility4 and to introduce functional groups. The Hummers method5 followed by reduction6 is a well-known way to produce reduced graphene oxide, a graphene derivative, which contains functional groups for further modification. Chua and co-workers have performed Friedel-Crafts alkylation and acylation reactions on reduced graphene oxide7. In these reactions, new C—C bonds are formed and the introduction of functional groups is mediated through this linker chain. Other methods include covalent coupling of functional groups to the basal plane of the graphene sheet using e.g. Diels-Alder reactions8 or diazonium chemistry9, or non-covalent adhesion via π-π stacking10, 11. However, many of these treatments compromise a characteristic feature of graphene: its two-dimensional structure, and most involve disruption of the graphene π-system, thus changing its electrical properties.
Other attempts to achieve successful edge functionalization of graphene have focused on planetary ball milling techniques12, 13, 14, 15. However, the high-energy, indiscriminate nature of these techniques, in which functionalization is performed in-situ during milling of the graphite starting material, has a number of drawbacks, most notably a lack of chemical control over the functional groups that are ultimately introduced.
In view of the above-discussed deficiencies, there remains a need for a controlled, more direct means of chemically modifying graphene, whilst simultaneously preserving its interesting and desirable properties for exploitation in further synthesis and applications.
The present invention was devised with the foregoing in mind.